Peristaltic pumps in general comprise a housing having a backing plate and an upstanding arcuate wall against which a section of flexible tubing is placed. The pump comprises in addition a rotatable pump head which is removably mounted on a shaft connected to a suitable drive means, which can be, for example, a DC motor. The pump head includes at least one rotatable roller means which, as the pump head rotates, squeezes the aforementioned section of flexible tubing against the arcuate wall of the pump. The progressive squeezing of the section of flexible tubing between the rotating roller means and the arcuate backing wall displaces a liquid contained in the lumen of the section of flexible tubing. The fluid is displaced ahead of the roller means, that is, the displacement of fluid in the flexible tubing corresponds to the direction of rotation of the pump head. Preferably, the pump head comprises two roller means, one of which begins engaging the section of flexible tubing at about the time the other is ending its engagement therewith.
As indicated above, the pump head, which rotates during use, is removably mounted on a pump shaft which is connected to a suitable drive means. The pump shaft has an opening extending inwardly from its top end. The pump head has a centrally located opening and is mounted in the pump by placing it over the pump shaft. It is conventional for the upper surface of the pump head to carry a pivotally mounted handle comprising an arm and a gripping means. The pump head is mechanically coupled to the pump shaft by pivoting the handle means so that its arm engages the opening in the upper end of the shaft. With the pump head thus mechanically coupled to the shaft, rotation of the pump shaft imparts the desired rotary motion to the pump head.
Peristaltic pumps have found use in a variety of medical applications such as blood dialysis and blood oxygenation. In dialysis, for example, a peristaltic pump is used for continuously removing blood from a patient having kidney disease, conveying the removed blood through an extracorporeal circuit including a blood conduit and an artificial kidney where the blood is purified, and returning the purified blood to the patient. In the case of open heart surgery, a blood oxygenator is employed to take over the gas exchange function of the lungs. In this case, the peristaltic pump is used for removing blood from the patient undergoing surgery, conveying the removed blood through an extracorporeal circuit including a blood conduit and a blood oxygenator, and returning the removed blood to the patient after oxygenation.
A patient undergoing dialysis or blood oxygenation might be seriously endangered if the pump being used to convey the patient's blood were to stop functioning owing, for example, to a power failure. In such case, it is highly desirable to be able to manually operate the pump head so that the pumping of blood will not be interrupted. In addition, it is usually desirable to be able to manually operate the pump head when the section of flexible tubing used with the pump is being inserted into position between the arcuate backing wall and the roller or rollers comprising the pump head. Means are usually provided, therefore, for enabling an operator to manually rotate the pump head in the event of a power or other failure or while setting up the extracorporeal circuit prior to beginning a medical or surgical procedure. These means quite commonly include a handle pivotally attached to the upper surface of the pump head. In the event it becomes necessary or desirable to manually operate the pump, this handle means is brought into its operative position at an angle to the upper surface of the pump head and is used to manually rotate the pump head.
If it is necessary to resort to manual operation of a pump during the course of a medical or surgical procedure, care must be taken that the pump head is rotated in the proper direction. In other words, the pump head must be rotated so that blood coming from the patient's arterial system is directed to the inlet of the pump, then through the section of flexible tubing to the outlet of the pump, and finally from the outlet of the pump to the venous return of the patient. Inadvertent rotation of the pump head in a direction which pumps blood in the reverse sense, that is, in a direction from the blood outlet to the blood inlet of the pump, must be avoided.
In the circumstances surrounding a power or other pump failure, and where it is necessary to operate the pump manually, an additional responsibility rests on those operating the pump and its associated equipment to see that the flow of blood is maintained in the proper direction. It is highly beneficial then if the pump includes means which prevent rotation of the pump head in a direction which would convey blood toward the inlet of the pump rather than towards its outlet.
As mentioned earlier, it is known to mechanically couple the pump head with the pump shaft by providing a handle on the pump head which can be pivoted into engagement with an opening in the upper portion of the pump shaft. In order to insure proper operation of the pump, there should be no tendency of the pump head to move upwardly on, or to lift off, the pump shaft. Hence, it is highly desirable that the pump include means for preventing the pump head from moving upwardly on the pump shaft when the shaft and the mechanically coupled pump head are being driven by an external power source such as an electric motor.